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Abstract Human urine is a readily available nutrient source that can complement commercial fertilizer production, which relies on finite mineral resources and global supply chains. This study evaluated the effectiveness of a simplified solar distillation process for urine to recover phosphorus (P) and nitrogen for agricultural use and water for non-potable purposes. Synthetic fresh, synthetic hydrolyzed, real fresh, and real hydrolyzed urine were exposed to direct sunlight for 6 h in a simple distillation apparatus, which produced distillation bottoms and distillate. Metal phosphate precipitation in the distillation bottoms was evaluated to recover P. The non-potable water was recovered as distillate. Hydrolyzed urine recovered more metal phosphate solid in the distillation bottoms and had a higher conductivity in the distillate than fresh urine. Hydrolyzed urine also achieved greater distillate volume recovery than fresh urine. Hydrolyzed urine had a greater presence of UV-absorbing organics in the distillate than fresh urine and therefore produced a lower-quality product water. There was no significant correlation between the daily high air temperature and the volume of distillate recovered. This study provides a comprehensive data set on simplified solar distillation of human urine considering the fate of nutrients and water for different types of urine.
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Emerging investigator series: thermodynamic and energy analysis of nitrogen and phosphorous recovery from wastewaters
In a circular nutrient economy, nitrogen and phosphorous are removed from waste streams and captured as valuable fertilizer products, to more sustainably reuse the resources in closed-loops and simultaneously protect receiving aquatic environments from harmful N and P emissions. For nutrient reclamation to be competitive with the existing practices of N fixation and P mining, the methods of recovery must achieve at least comparable energy consumption. This study employed the Gibbs free energy of separation to quantify the minimum energy required to recover various N and P fertilizer products from waste streams of fresh and hydrolyzed urine, greywater, domestic wastewater, and secondary treated wastewater effluent. The comparative advantages in theoretical energy intensities for N and P recovery from nutrient-dense waste streams, such as fresh and hydrolyzed urine, were assessed against the other more dilute sources. For example, compared to reclaiming the nutrients from treated wastewater effluent at centralized wastewater treatment plants, the minimum energy required to recover 1.0 M NH 3(aq) from source-separated hydrolyzed urine can be ≈40–68% lower, whereas recovering KH 2 PO 4(s) from diverted fresh urine can, in principle, be ≈13–34% less energy intensive. The study also evaluated the efficiencies required by separation techniques for the energy demand of N and P recovery to be lower than the current production approaches of the Haber–Bosch process and phosphate rock mining. For instance, the most energetically favorable ammoniacal nitrogen and orthophosphate reclamation schemes, which target hydrolyzed and fresh urine, respectively, require energy efficiencies >7% and >39%. This study highlights that strategic selection of waste stream and fertilizer product can enable the most expedient recovery of nutrients and realize a circular economy model for N and P management.
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- Award ID(s):
- 1903705
- PAR ID:
- 10358582
- Date Published:
- Journal Name:
- Environmental Science: Water Research & Technology
- Volume:
- 7
- Issue:
- 11
- ISSN:
- 2053-1400
- Page Range / eLocation ID:
- 2075 to 2088
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1EW00554E
